The present invention relates to a pretreatment process of a zeolite catalyst and a process for producing an alcohol using the pretreated zeolite catalyst. The pretreated zeolite catalyst is useful for the production of alcohols through hydration of olefins.
Hydration of olefins in a homogeneous system in the presence of a catalyst such as a mineral acid or the like has been generally employed for the industrial production of alcohols. In recent years, the alcohol production processes using a solid acid catalyst, especially a zeolite as catalyst for the hydration have been proposed in place of the conventional process (For example, Japanese Patent Application Laid-Open (KOKAI) Nos. 57-70828 (1982), 58-124723 (1983) and 58-194828 (1983)).
However, it is difficult to obtain a sufficient catalyst activity even by using a zeolite as catalyst, and in order to obtain a reaction rate well satisfactory for the industrial process, it is necessary to raise the reaction temperature. Hydration of olefins is usually exothermic, and the ratio of alcohol to olefin at equilibrium decreases with rise of temperature.
Therefore, rise of reaction temperature leads to a reduced concentration of alcohol as the product, and as a consequence, a great deal of cost is required for separation and recovery of olefin as the starting material and alcohol as the product. Further, rise of reaction temperature causes a corresponding elevation of not only the hydration rate of the olefin but also the rate of its conversion to the by-products through side reactions such as isomerization, which may result in a reduced selectivity of the hydration.
By the studies for overcoming the above problems, the present inventors have found that by using as a catalyst of hydration of an olefin, zeolite which has been kept in contact with water, the hydration can be proceed with remarkably high catalytic activity as compared with the conventional process. The present invention has been attained based on the finding.